Fair Value Measurement - Financial Instruments Carried at Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Assets:
Fixed-maturity securities		$ 11,047	$ 11,023
Other invested assets		167	169
Credit derivative assets		55	81
Liabilities:
Credit derivative liabilities		489	446
Investment funds, fair value		45	45
Recurring [Member]
Assets:
Other invested assets	[1]	12	12
Credit derivative assets		55	81
FG VIEs’ assets, at fair value		1,191	1,261
Other assets		93	106
Total assets carried at fair value		12,398	12,483
Liabilities:
Credit derivative liabilities		489	446
FG VIEs’ liabilities with recourse, at fair value		1,165	1,225
FG VIEs’ liabilities without recourse, at fair value		119	124
Total liabilities carried at fair value		1,773	1,795
Recurring [Member] | Level 1 [Member]
Assets:
Other invested assets	[1]	0	0
Credit derivative assets		0	0
FG VIEs’ assets, at fair value		0	0
Other assets		26	23
Total assets carried at fair value		358	328
Liabilities:
Credit derivative liabilities		0	0
FG VIEs’ liabilities with recourse, at fair value		0	0
FG VIEs’ liabilities without recourse, at fair value		0	0
Total liabilities carried at fair value		0	0
Recurring [Member] | Level 2 [Member]
Assets:
Other invested assets	[1]	5	5
Credit derivative assets		0	0
FG VIEs’ assets, at fair value		0	0
Other assets		21	21
Total assets carried at fair value		9,661	9,600
Liabilities:
Credit derivative liabilities		0	0
FG VIEs’ liabilities with recourse, at fair value		0	0
FG VIEs’ liabilities without recourse, at fair value		0	0
Total liabilities carried at fair value		0	0
Recurring [Member] | Level 3 [Member]
Assets:
Other invested assets	[1]	7	7
Credit derivative assets		55	81
FG VIEs’ assets, at fair value		1,191	1,261
Other assets		46	62
Total assets carried at fair value		2,379	2,555
Liabilities:
Credit derivative liabilities		489	446
FG VIEs’ liabilities with recourse, at fair value		1,165	1,225
FG VIEs’ liabilities without recourse, at fair value		119	124
Total liabilities carried at fair value		1,773	1,795
Fixed Maturities [Member]
Assets:
Fixed-maturity securities		10,588	10,627
Fixed Maturities [Member] | Obligations of state and political subdivisions [Member]
Assets:
Fixed-maturity securities		5,776	5,841
Fixed Maturities [Member] | US government and agencies [Member]
Assets:
Fixed-maturity securities		405	400
Fixed Maturities [Member] | Corporate securities [Member]
Assets:
Fixed-maturity securities		1,525	1,520
Fixed Maturities [Member] | RMBS [Member]
Assets:
Fixed-maturity securities	[2]	1,239	1,245
Fixed Maturities [Member] | CMBS [Member]
Assets:
Fixed-maturity securities	[2]	556	513
Fixed Maturities [Member] | Asset-backed Securities [Member]
Assets:
Fixed-maturity securities		811	825
Fixed Maturities [Member] | Foreign government securities [Member]
Assets:
Fixed-maturity securities		276	283
Fixed Maturities [Member] | Recurring [Member]
Assets:
Fixed-maturity securities		10,588	10,627
Fixed Maturities [Member] | Recurring [Member] | Obligations of state and political subdivisions [Member]
Assets:
Fixed-maturity securities		5,776	5,841
Fixed Maturities [Member] | Recurring [Member] | US government and agencies [Member]
Assets:
Fixed-maturity securities		405	400
Fixed Maturities [Member] | Recurring [Member] | Corporate securities [Member]
Assets:
Fixed-maturity securities		1,525	1,520
Fixed Maturities [Member] | Recurring [Member] | RMBS [Member]
Assets:
Fixed-maturity securities		1,239	1,245
Fixed Maturities [Member] | Recurring [Member] | CMBS [Member]
Assets:
Fixed-maturity securities		556	513
Fixed Maturities [Member] | Recurring [Member] | Asset-backed Securities [Member]
Assets:
Fixed-maturity securities		811	825
Fixed Maturities [Member] | Recurring [Member] | Foreign government securities [Member]
Assets:
Fixed-maturity securities		276	283
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | Obligations of state and political subdivisions [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | US government and agencies [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | Corporate securities [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | RMBS [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | CMBS [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | Asset-backed Securities [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 1 [Member] | Foreign government securities [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Fixed-maturity securities		9,508	9,543
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | Obligations of state and political subdivisions [Member]
Assets:
Fixed-maturity securities		5,769	5,833
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | US government and agencies [Member]
Assets:
Fixed-maturity securities		405	400
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | Corporate securities [Member]
Assets:
Fixed-maturity securities		1,451	1,449
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | RMBS [Member]
Assets:
Fixed-maturity securities		879	897
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | CMBS [Member]
Assets:
Fixed-maturity securities		556	513
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | Asset-backed Securities [Member]
Assets:
Fixed-maturity securities		172	168
Fixed Maturities [Member] | Recurring [Member] | Level 2 [Member] | Foreign government securities [Member]
Assets:
Fixed-maturity securities		276	283
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Fixed-maturity securities		1,080	1,084
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | Obligations of state and political subdivisions [Member]
Assets:
Fixed-maturity securities		7	8
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | US government and agencies [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | Corporate securities [Member]
Assets:
Fixed-maturity securities		74	71
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | RMBS [Member]
Assets:
Fixed-maturity securities		360	348
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | CMBS [Member]
Assets:
Fixed-maturity securities		0	0
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | Asset-backed Securities [Member]
Assets:
Fixed-maturity securities		639	657
Fixed Maturities [Member] | Recurring [Member] | Level 3 [Member] | Foreign government securities [Member]
Assets:
Fixed-maturity securities		0	0
Short-term Investments [Member]
Assets:
Fixed-maturity securities		459	396
Short-term Investments [Member] | Recurring [Member]
Assets:
Fixed-maturity securities		459	396
Short-term Investments [Member] | Recurring [Member] | Level 1 [Member]
Assets:
Fixed-maturity securities		332	305
Short-term Investments [Member] | Recurring [Member] | Level 2 [Member]
Assets:
Fixed-maturity securities		127	31
Short-term Investments [Member] | Recurring [Member] | Level 3 [Member]
Assets:
Fixed-maturity securities		$ 0	$ 60

[1] Excluded from the table above are investments funds of $45 million and $45 million as of March 31, 2016 and December 31, 2015, respectively, measured using NAV per share. Includes Level 3 mortgage loans that are recorded at fair value on a non-recurring basis.

[2] Government-agency obligations were approximately 52% of mortgage backed securities as of March 31, 2016 and 54% as of December 31, 2015 based on fair value.